History effect in inhomogeneous superconductors

TL;DR

This paper introduces a model explaining a new history effect in inhomogeneous superconductors, linking flux pinning inhomogeneity and flux creep to observed V-I loop behaviors under varying conditions.

Contribution

It presents a novel model combining flux pinning inhomogeneity and flux creep to explain history effects and predicts V-I loop behaviors at different sweeping rates and magnetic fields.

Findings

V-I loops exhibit clockwise behavior consistent with the model.

Loop area is more sensitive to sweeping rate than magnetic field.

Experimental results align with numerical predictions.

Abstract

A model was proposed to account for a new kind of history effect in the transport measurement of a sample with inhomogeneous flux pinning coupled with flux creep. The inhomogeneity of flux pinning was described in terms of alternating weak pinning (lower jc) and strong pinning region (higher jc). The flux creep was characterized by logarithmic barrier. Based on this model, we numerically observed the same clockwise V-I loops as reported in references. Moreover, we predicted behaviors of the V-I loop at different sweeping rates of applied current dI/dt or magnetic fields Ba, etc. Electric transport measurement was performed in Ag-sheathed Bi2-xPbxSr2Ca2Cu3Oy tapes immersed in liquid nitrogen with and without magnetic fields. V-I loop at certain dI/dt and Ba was observed. It is found that the area of the loop is more sensitive to dI/dt than to Ba, which is in agreement well with our numerical results.